In case debootstrap complains about a missing script, download the current version ​http://ftp.debian.org/debian/pool/main/d/debootstrap/ and run that executable directly
$> sudo /home/USER/debootstrap-1.0.53/debootstrap --foreign --variant=buildd --arch=amd64 saucy ./13.10_amd64
in newer versions of debootstrap you have to run the second stage maually
$> sudo /home/USER/debootstrap-1.0.53/debootstrap --second-stage

It is highly recommended to manage the chroots using schroot. See the general build server setup page for information on how to set it up.

RECOMMENDED: You can also use debootstrap on a nother system (first stage), copy the result to the target system (build server)

Rock packages may depend on non-main packages, so you need to make sure that these are included in your sources. On Debian, /etc/apt/sources.list should read like something around the lines of

deb http://ftp.de.debian.org/debian testing main contrib non-free

On Ubuntu, it should look like

deb http://archive.ubuntu.com/ubuntu precise main universe multiverse

When the chroot is Debian and the host not, it happens that the 'staff' and 'crontab' groups do not exist in the chroot (you get an error when installing some packages). Creating the group in the chroot is of no use as schroot copies this file each time you log in. Either add the group to the host, or disable copying